Just remembering what I saw when I was looking for our SJ23 2 years
ago...pretty much depends on the condition of the boat. We have a 1977,
but I've seen boats 5 years younger that looked 10 years older (and hence
weren't worth but half what we paid for ours). I think once they're over
20 years old depreciation pretty much hits a plateau unless you do some major
damage to it or are missing major pieces of equipment. Likewise you
might be able to get a little bit more if you make some nice upgrades that
appeal to the right buyer. I would think if you picked up an SJ23 over
20 years old and took good care of it, you should be able to turn it over for
pretty much what you paid for it anytime, provided your market did not change
drastically.